Method of burning pulverized fuel



Sept. 24, 1929. J. E. BELL 1,729,024

METHOD OF BURNING PULVERIZED FUEL Filed Dec. 9, 1921 4 Sheets-Sheet 1 Sept. 24, 1929. BELL 1,729,024

METHOD OF BURNING PULVERIZED FUEL iled 9, 1921 4 Sheets-Sheet 2 avweutoz Sept. 24, 1929. J. E. BELL METHOD OF BURNING PULVERIZED FUEL Fil Dec. 1921 4 Sheets-Sheet 3 alga.

Sept. 24, 1929. J. E. BELL 1,729,024

METROD 0F BURNING PULVERIZED FUEL Filed 1921 4 Sheets-Sheet 4 I w// H/ m m m m m m m Q m m m m m m m n s m m m [:JEIIIIIIIIIIICIIIICIEIIIIIII Patented Sept. 24, 1929 UNITED STATES PATENT OFFICE JOHN E BELL, OF BROOKLYN, NEW YORK, ASS IGNOR TO COMBUSTION ENGINEERING CORPORATION, A CORPORATION OF NEW YORK METHOD OF BURNING PULVEBIZED FUEL Application filed December 9, 1921.

This invention relates to a method of and apparatus for burning pulverized fuel and is particularly useful in connection with the generation of steam.

One of the primary objects of my invention is to promote more perfect combustion and to obtain the greatest possible degree of ellicieucy.

Another object of my invention is the provision of a method and apparatus whereby more fuel can be consumed in a furnace of given size within a given time: or, stated in another way. greater horsepower may be developed in a furnace of given size.

The foregoing,- togetber with such other objects as may hereinafter appear or are incident to my invention. I obtain by means of a method and apparatus illustrated in preferred form in the accompanying drawings whereiu:Fig. 1 is a longitudinal vertical section through a furnace embodying my improvements and adapted to carry out my process: Fig. 2 is a section on the line 2-2 of Fig. 1: Fig. 3 is a section on the line 3-3 of Fig. 1 Fig. 4 is a diagrammatic view illustrating the manner in which combustion takes place: and Fig. 5 is a section illustrating a modification of my invention.

The uethod and apparatus will be de- -scribed together. as the former will be understood from a description of thclatter.

Referring now to Figs. 1 to 3 inclusive, it will be seen that the furnace there illustrated is substaut ially rectangular in horizon tal cross section. The outlet 7 from the combustion chamber 8 is substantially centrally located in the top wall 9. 1n the bottom of the combustion chamber. below the outlet 7.

there is a substantially centrally located connoidal portion 11) composed of suitable refractory material. Fuel is admitted on all four sides of the combustion chamber in a substantially vertically downward direction by means of the burners ll. of which there are preferably three on each side and the construction of which will be later described. Air is admitted by induction through all side walls of the combustion chamber by means of the rows of damper controlled inlets 12.

v There are a number of such rows vertically,

Serial No. 521,273.

and the inlets of one row are preferably staggered with respect to the adjacent row. The side walls are cut back near the bottom to provide an annular reentrant portion 13, and the conoidal portion 10 is similarly cut back to provide a reentrant portion 14 extending thereabout. A coil of pipe 15 is located in the reentrant portion 13 and a similar coil of pipe 16 in the reentrant portion 14. A cooling circulation is maintained through such coils of pipe.

The boiler installation above the outlet 7 is preferably of the tubular type and includes the upper drums 17 the lower drums 18 and the banks of tubes 19. The outlets from the boiler chamber to the stack (which is not shown) are indicated at 20. The hot gases take a battled course through the banks of tubes in any preferred manner. Referring now to the urners. it will be seen that the lower portion of each burner is divided into two chambers by a wall or septum 21, the burner proper 22 extending downwardly into one of said chambers. the air supply of which is controlled by the dampers 22. The other chamber 23 has its supply of air controlled by the main damper 24. The burner is of the fishtail type and is adapted to deliver a thin, sheet-like stream of fuel or a mixture of fuel and air. An embracing envelope of air is induced through the dampers 22, and a flow of air through the chamber 23 is also induced. such stream of air being on the side of the stream of fuel next the outlet or draft. The operation is as follows:

The pulverized fuel or mixture of pulverized fuel and air is discharged from the burners. preferably by gravity, in the. form of thin sheets. each sheet being surrounded by an envelope of air. These sheets or streams of fuel and air increase in width so that the three streams on each side merge into one another to form a large sheet. substantially coextensive with the respective side of the furnace. The large streams or sheets merge together at the corners.

The downwardly descending streams of fuel, once the furnace has become sufiiciently heated, are subjected to radiant heat from the side or vertical walls and also from the center,

as will further appear, and ignite. Since the incoming streams are in sheet form, it will be seen that a maximum area is presented for the absorption of radiant heat. and ignition takes place and is completed more rapidly. In addition to this it will also be seen that when the. fuel is delivered in this form. particularly with its surrounding envelope of air. each particle of fuel will be more or less surrounded by air necessary to initiate ignition. As the particles burn and gasify. additional air is required to complete combustion and this is supplied by induction through the inlets 12 through which bodies of air surrounding the fuel and flame stream (considered as a single body) are drawn. The air necessary to complete combustion on the inside. that is to say on the draft side of the downwardly descending streams. is supplied through the channels or chambers 23.

The draft turns the downwardly descending fuel and flame streams inwardly and upwardly back on themselves. as is diagrammatically indicated in Fig. l. The path of each sheet, considered singly. is therefore roughly that of a U. The downwardly descending portions of a stream. therefore. are subject to the radiant heat of the ascending portions.

It will be seen from the foregoing that the central portion of the combustion chamber is entirely filled with a mass of flame. substantially rectangular in cross section. the edges of such central mass of flame coming fairly close to the downwardly descending fuel stream. At the same time the additional air required for combustion is supplied in such manner that oxygen laden air is always available as combustion progresses from start to finish. The air that is admitted through the inlets 12 follows the stream line of the fuel and flame. bordering the latter on the outside and bending therewith and moving toward the center as the draft bends the fuel and flame stream back on itself. Into this hordering stream of air the heavier unconsmned particles of fuel gravitate out of the main fuel and flame stream and find the necessary oxygen for completing combustion. and as gasif'ication and expansion progressively increase with concomitant setting up of eddies. the gases are continually brought into contact with fresh oxygen bea ring air. Similarly on the inside of the U, the air needed is supplied through the chambers 23 and through the upper row or rows of inlets 12 which a re above the meeting or merging of the individual small streams into the large streams.

The combustion chamber is of sufficiently large size as to permit of the complete combustion of the fuel therein. The point at which the streams turn back on themselves mav be regulated by means of the dampers which through the channels 23. If the momentum be increased. the streams will be turned lower down in the furnace and vice versa if the momentum be decreased, the streams will then turn themselves at a higher level.

I prefer to turn the streams at some distance above the bottom of the combustion chamber so that the refuse gravitating out of the fuel and flame stream will be in the form of a floeculent ash which will readily find its way through the opening 25 to the ashpit. The slag that forms on theside walls will drip therefrom at the reentrant portion 13 in the form of nodules which will be cooled by the action of the cooling coil 15. Such nodules will remain in individual state and will not coalesce with others. They will work themselves out through the openings 25 and are readily removed from the ashpit. Similarly, should there be any slag formed on the surface of the conoidal portion 10, this will drip off and be cooled by the coil 16 in a similar manner.

The conoidal portion 10 reflects and radiatcs heat out and into the central mass of flame. thus tending to increase efficiency by securing more perfect combustion.

It will be seen from the foregoing that a maximum portion of the volume of the combustion chamber is utilized for combustion purposes. dead spaces. i. e., spaces in which no flame is present, being reduced to a minimum. Thus the size of a furnace necessary to produce a given horsepower may be reduced. or stated in another way it is possible to burn more fuel and generate more steam in a given furnace in a shorter length of time and with less fuel. It will also be seen that as a result of my improvement the total length of time necessary to achieve complete combustion is considerably cut down, which makes it possible to decrease the over all height of the furnace.

In the installation shown in Fig. 5, the construetipn and operation is substantially the same with two exceptions. In place of the conoidal portion 10 T have substituted a. pyramidal portion 10. By turning the stream sufficiently high to allow the ash depositing on the pyramidal portion to remain below slag forming temperature and by making the slope sharper than the angle of rest, the )yramid will be self cleaning. The boiler setting is of the horizontal type, with the tubes suitably baflled.

I claim:

1. The herein described rocess of burning pulverized fuel in suspension which consists in admitting the fuel in the formof an attenuated stream at each of the four sides of the furnace in a substantially downward direction and in turning the streams inwardly and u wardly.

2. he herein described process of burning pulverized fuel in suspension whic consists in admitting the fuel in the form of an attenuated stream at each of the four sides of the furnace in a substantially downward dimy name.

JOHN E. BELL. 

